Radikal Therapeutics (RTX) is developing a first-in-class cytoprotective small molecule (R-801) for the prevention of spinal cord injury (SCI) based upon the chemical fusion of 2 discrete chemical domains that: 1) target redox stress via a nitroxide spin-trap moiety, and 2) trigger the endogenous ischemic-preconditioning response via mitochondrial-selective K+-ATP channel activation. We have confirmed a powerful effect of R- 801 in rodent models of trauma, including hemorrhagic shock and ischemia reperfusion injury of the heart, lung, limb, and kidney. In a pilot study of spinal cord trauma (SCT), resuscitation of mice with R-801 produced an accelerating and non-plateauing improvement in motor function (20% total recovery over the first 10 days). R-801 has shown no evidence of toxicity in rodents and large animals. At present, R-801 is the first and only safe, effective, and selective mito-K+-ATP channel opener in development, as no other firm or academic center has succeeded to date in inventing a safe, effective, and selective mito-K+-ATP channel opener. We now propose to verify the pre-clinical feasibility of R-801 in a classic model of SCT and to deepen the understanding of its mechanism of action. Phase 1 SBIR Specific Aim: Establish the PD profile of R-801 in an experimental murine model of SCI. In order to test the hypothesis that R-801 effectively resuscitates SCT, RTX will carry out a pathologic and functional analysis in a prospective, randomized, single-blinded, placebo-controlled investigation in mice. In collaboration with Professor Philip Popovich (Ohio University), adult female CD1 mice will be subjected to SCT using a standardized model of contusion injury. Sham injury (laminectomy without SCT) and vehicle control groups will be compared to a group receiving R-801. The initial 2 doses of R-801 (80 mg/kg/dose), given 1 and 3 h after SCT, will be administered intraperitoneally (IP) in order to obtain a rapid tissue penetration of high levels of the drug int spinal cord tissue. Thereafter, R-801 will be provided in the drinking water (as a 0.2% solution) in order to optimize steady-state drug exposure. In Series A, mice (n=10 per group) will be sacrificed 48 h after SCT for histologic and immunohistochemical analysis of the spinal cord for evidence of of poly(ADP-ribose) polymerase activation and ONOO- formation. In Series B, open field locomotor function will be analyzed in adult female SCI mice (n=10 per group) for a period of 2 months post SCT. Mice will be acclimated to the open field ~1 week prior to SCT. Indices of functional recovery will be measured using the Open field-testing (Basso Mouse Scale; BMS) locomotor rating scale. BMS scores will then be obtained pre-injury and again at weekly intervals. Terminal plasma concentrations of R-801 will be obtained, in order to construct a PD profile relating the efficacy in each dose group to functional, morphologic, and immunohistochemical endpoints. Verification that R-801 resuscitation ameliorates morphologic and functional outcomes will provide a logical foundation for commercial development of parenteral R-801 as an emergent therapy for acute SCI.